Significant progress has been made in recent years towards establishing atomic measurement standards for field quantities. Rydberg atoms hold particular appeal for applications in electrometry due to their large transition electric dipole moments, which lead to a strong atomic response to electric (E) fields. Rydberg electromagnetically induced transparency (EIT) in atomic vapors has recently been demonstrated by applicants as a practical approach to absolute measurements of radio-frequency (RF) E fields over a broad frequency range (10 MHz to 500 GHz) and dynamic range (˜100 mV/m to >1 kV/m) suitable for the development of calibration-free broadband RF sensors. The utility of the Rydberg EIT technique in characterizing RF E fields has been demonstrated in a number of applications. These include microwave polarization measurements, millimeter-wave (mm-wave) sensing, and subwavelength imaging. The approach has also been employed in room-temperature studies of multiphoton transitions in Rydberg atoms, as well as in measurements of static E fields for precise determinations of quantum defects.
The Rydberg EIT measurement technique has been employed in measurements of weak RF fields. In the weak-field regime, the atom-field interaction strength is small compared to the Rydberg energy-level structure, and the level shifts of the relevant coupled atom-field states are well described using perturbation theory. By exploiting near-resonant and resonant dipole transitions between high-lying Rydberg levels, which elicit a maximal atomic response, RF fields from as small as approximately 100 mV/m to a few tens of V/m have been measured. For measurements of strong RF E fields, the atom-field interaction cannot be modeled using perturbative methods and requires a non-perturbative method to accurately describe the response of the atomic system. Extending the atom-based measurement approach to a high-power regime could enable, for example, subwavelength characterizations of antennas radiating high-power microwaves among other applications.
This section provides background information related to the present disclosure which is not necessarily prior art.